CN109923748B

CN109923748B - Switching circuit and power supply device

Info

Publication number: CN109923748B
Application number: CN201780067697.6A
Authority: CN
Inventors: 森冈秀夫; 中村有延
Original assignee: Sumitomo Wiring Systems Ltd; AutoNetworks Technologies Ltd; Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Wiring Systems Ltd; AutoNetworks Technologies Ltd; Sumitomo Electric Industries Ltd
Priority date: 2016-11-15
Filing date: 2017-10-30
Publication date: 2022-02-22
Anticipated expiration: 2037-10-30
Also published as: CN109923748A; WO2018092563A1; US20200059084A1; JP2018082541A; JP6919180B2

Abstract

A switching circuit mounted on a wire connecting a plurality of storage batteries includes a semiconductor switch for turning on or off the connection between the storage batteries and a protection switch connected in parallel with the semiconductor switch. The protection switch has a pair of terminals connected to respective electric wires and a conductive plate formed by bonding a plurality of conductive members having different thermal expansion coefficients. The conductive plate deforms to connect the terminals with each other in accordance with a temperature rise of the semiconductor switch, and connects the power supplies with each other.

Description

Switching circuit and power supply device

Technical Field

The invention relates to a switching circuit and a power supply device.

The present application claims priority based on 2016 of Japanese patent application No. 2016-.

Background

Patent document 1 discloses a protection circuit in which a conductive member is provided on a substrate via a fusing member, and when a semiconductor switch generates heat abnormally, the fusing member fuses, whereby the conductive member is displaced on the substrate and comes into contact with two terminals provided on the substrate, thereby electrically connecting the terminals.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-131138

Disclosure of Invention

A switching circuit according to the present disclosure is a switching circuit mounted on an electric wire connecting a plurality of power sources, and includes: a semiconductor switch mounted on the wire to turn on or off connection between the plurality of power sources; and a protection switch connected in parallel with the semiconductor switch, and deformed in accordance with a temperature rise of the semiconductor switch, thereby turning on the connection between the power supplies.

The power supply device of the present disclosure includes a plurality of power supplies and the above-described switch circuit.

Drawings

Fig. 1 is a block diagram showing a configuration example of a power supply device according to embodiment 1.

Fig. 2A is a sectional view showing a configuration example of the protection switch according to embodiment 1.

Fig. 2B is a sectional view showing a configuration example of the protection switch according to embodiment 1.

Fig. 2C is a sectional view showing a configuration example of the protection switch according to embodiment 1.

Fig. 3A is a sectional view showing a configuration example of a protection switch according to embodiment 2.

Fig. 3B is a sectional view showing a configuration example of the protection switch according to embodiment 2.

Fig. 3C is a sectional view showing a configuration example of the protection switch according to embodiment 2.

Detailed Description

[ problem to be solved by the present disclosure ]

In the protection circuit disclosed in patent document 1, the terminals are electrically connected to each other by melting the melting member, and therefore the temperature at which the terminals are connected to each other (the temperature at which the protection circuit operates) is determined by the melting point of the melting member. However, it is not always possible to select a material that can achieve a desired melting point. For example, when the melting member needs to use a lead-free solder, it is difficult to adjust the melting point, and it is difficult to realize a melting member having a desired melting point. Therefore, it is not easy to arbitrarily set the temperature at which the protection circuit operates.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a switching circuit and a power supply device including a protection circuit that operates at an arbitrary temperature.

[ Effect of the present disclosure ]

According to the present disclosure, a switching circuit and a power supply device including a protection switch that operates at an arbitrary temperature can be provided.

[ description of embodiments of the invention ]

First, embodiments of the present invention will be described. At least some of the embodiments described below may be arbitrarily combined.

(1) A switching circuit according to an aspect of the present invention is mounted on a wire connecting a plurality of power sources, and includes: a semiconductor switch mounted on the wire to turn on or off connection between the plurality of power sources; and a protection switch connected in parallel with the semiconductor switch, and configured to be deformed in accordance with a temperature rise of the semiconductor switch, thereby connecting the power supplies.

In this embodiment, the protection switch provided in parallel with the semiconductor switch is deformed in accordance with the temperature rise of the semiconductor switch, thereby turning on the connection between the power supplies. In the protection switch in which the connection between the power sources is turned on by the deformation accompanying the temperature rise, the setting of the operating temperature is easier than in the structure in which the terminals are connected by the melting of the melting member. Therefore, a switching circuit including a protection switch that operates at an arbitrary temperature can be realized.

(2) Preferably, the protection switch has: terminal pairs respectively connected to the electric wires; and a conductive plate which is formed by bonding a plurality of conductive members having different thermal expansion coefficients, wherein the conductive plate is connected to one of the terminals of the pair of terminals and deforms to connect the one of the terminals of the pair of terminals to the other of the terminals in accordance with a temperature rise of the semiconductor switch.

In this aspect, the protection switch is constituted by a conductive plate in which a plurality of conductive members having different thermal expansion coefficients are bonded. The conductive plate deforms as the temperature of the semiconductor switch rises, and the deformed conductive plate connects the terminals. For example, a bimetal formed by bonding two kinds of metal films can easily set the temperature at the time of deformation, and thus a protection switch that operates at an arbitrary temperature can be realized.

(3) Preferably, at least the other terminal of the pair of terminals is formed of a melting member having conductivity and melting at a predetermined temperature.

In this embodiment, the terminal to which the protection switch that operates (deforms) is connected is formed of a melting member that melts at a predetermined temperature. Therefore, when the temperature is equal to or higher than the predetermined temperature, the terminal of the melting member melts, and the resistance of the terminal can be reduced.

(4) Preferably, when the connection between the power sources is turned on, the protection switch is deformed to return to its original shape as the temperature of the semiconductor switch decreases, thereby turning off the connection between the power sources.

In this aspect, the operating protection switch returns to its original shape as the temperature of the semiconductor switch decreases, thereby disconnecting the power supplies. Therefore, when the temperature of the semiconductor switch decreases due to the operation of the protection switch, the connection between the power supplies by the protection switch is cut off, and only the connection between the power supplies by the semiconductor switch is performed.

(5) Preferably, the protection switch turns off the connection between the power supplies at a temperature lower than a temperature at which the connection between the power supplies is turned on.

In this aspect, the protection switch turns off the connection between the power supplies at a temperature lower than a temperature at which the connection between the power supplies is turned on. Therefore, in the case where the power supplies are temporarily connected by the protection switch, the connection between the power supplies is maintained until the temperature at which the connection between the power supplies is turned off is reduced, and therefore it is possible to prevent the connection between the power supplies from being frequently turned on/off.

(6) A power supply device according to an aspect of the present invention includes: a plurality of power supplies; and any one of the above switching circuits.

In this embodiment, a plurality of power sources are connected via a switch circuit including a protection switch that operates at an arbitrary temperature.

[ details of embodiments of the present invention ]

In recent years, a power supply system including a plurality of storage batteries is mounted on a vehicle. In such a power supply system, a switch for turning on/off the electrical connection between the storage batteries is provided. Since the switch provided between the batteries is frequently turned on/off, a semiconductor relay (semiconductor switch) having a longer opening/closing life than a mechanical relay is used. On the other hand, when a semiconductor switch is used, if an excessive current flows in the switch due to a short circuit or the like, the semiconductor element generates heat, and the semiconductor element itself and peripheral components may be damaged by the heat generation. Therefore, in the case of using a semiconductor switch, there is provided a structure in which the switch is turned off before components constituting the switch rise to a heat-resistant temperature. In addition, a protection circuit is also provided which protects the switch in the event of an accident without being able to turn it off. For example, the protection circuit is configured to be connected in parallel with the semiconductor switch, and to reduce the current flowing to the semiconductor switch by shunting the current flowing to the semiconductor switch to the protection circuit.

A switching circuit and a power supply device according to an embodiment of the present invention will be described below with reference to the drawings showing the embodiments. The present invention is not limited to these examples, and is intended to cover modifications within the scope of the claims, which include equivalents to the claims and all modifications within the scope of the claims.

(embodiment mode 1)

Fig. 1 is a block diagram showing a configuration example of a power supply device according to embodiment 1. The power supply device according to embodiment 1 is mounted on a vehicle. The power supply device of embodiment 1 includes two first batteries 41 and two second batteries 43 (power supplies), and has a switch circuit 1 mounted on an electric wire 40 connecting the

batteries

41 and 43. The

batteries

41 and 43 are connected in parallel via the switch circuit 1. The power supply device mounted on the vehicle may be configured to include three or more storage batteries, and in this case, a switch circuit is mounted on an electric wire connecting between the storage batteries.

In the power supply device according to embodiment 1, a load 42 as an in-vehicle device such as a navigation system is connected in parallel to the first battery 41. A starter 44 for starting the engine of the vehicle is connected in parallel to the second battery 43. The first battery 41 and the second battery 43 may be connected in parallel with a load other than the load 42 and the starter 44.

The switching circuit 1 includes: a semiconductor switch 2 mounted on the electric wire 40 and turning on or off the connection between the

batteries

41 and 43; a switch control unit 20 that controls turning on or off of the semiconductor switch 2; and a protection switch 3 connected in parallel with the semiconductor switch 2. Fig. 1 shows an example in which the semiconductor switch 2 is formed of an N-channel FET (Field Effect Transistor), but the semiconductor switch 2 may be formed of a P-channel FET.

The switch control unit 20 turns off the semiconductor switch 2 when the connection between the first battery 41 and the second battery 43 should be disconnected. For example, when the starter 44 starts the engine, a notification signal is input to the switch control unit 20 in advance. When the notification signal is input, the switch control unit 20 turns off the semiconductor switch 2 to disconnect the first battery 41 and the second battery 43.

Since the starter 44 requires a large amount of current when starting the engine, a large voltage variation occurs when starting the engine. Therefore, as described above, before the engine is started by the starter 44, the connection between the first battery 41 and the second battery 43 is disconnected so that the influence of the voltage fluctuation generated on the starter 44 (second battery 43) side does not reach the first battery 41 and the load 42.

After the voltage of the second battery 43 is restored, the switching control unit 20 turns on the semiconductor switch 2, and resumes the connection between the first battery 41 and the second battery 43. In the normal state, the switch control unit 20 turns on the semiconductor switch 2, and thereby the electric power from the two

batteries

41 and 43 is supplied to the load 42 and the like in the normal state.

In the power supply device according to embodiment 1, for example, when a short circuit occurs on the second battery 43 side, a large current flows from the first battery 41 through the semiconductor switch 2 and the short-circuit path. When a large current flows through the semiconductor switch 2, the semiconductor element constituting the semiconductor switch 2 generates heat, the semiconductor element itself and peripheral components are overheated, and the components may be damaged.

Therefore, in the power supply device according to embodiment 1, the protection switch 3 is operated before each member becomes an overheated state, and the connection between the

storage batteries

41 and 43 via the protection switch 3 is established. When the protection switch 3 is operated, a large current flowing to the semiconductor switch 2 is shunted to the protection switch 3, and therefore the current flowing to the semiconductor switch 2 can be reduced. As a result, heat generation of the semiconductor element can be suppressed, and damage to the respective members can be prevented.

Fig. 2A to 2C are sectional views showing a configuration example of the protection switch 3 according to embodiment 1. Fig. 2A shows the protection switch 3 in an off state (non-operating state), and fig. 2B and 2C show the protection switch 3 in an on state (operating state).

The protection switch 3 according to embodiment 1 is provided between

bus bars

51a and 51b separately formed on a substrate 50. The bus bars 51a, 51b are made of a conductive material, and the electric wires 40 are connected to the

bus bars

51a, 51b, respectively. For example, in the electric wires 40 shown in fig. 1, the electric wire 40 connected to the left side of the switch circuit 1 is connected to the bus bar 51a, and the electric wire 40 connected to the right side of the switch circuit 1 is connected to the bus bar 51 b. In such a configuration, the protection switch 3 turns on or off the connection between the bus bars 51a and 51b, thereby turning on or off the connection between the

batteries

41 and 43 via the electric wire 40. The semiconductor switch 2 is also provided to turn on or off the connection between the bus bars 51a and 51 b.

Specifically, the protection switch 3 includes: a first terminal 31 provided on an upper surface of the bus bar 51 a; a second terminal 32 provided on an upper surface of the bus bar 51 b; and a rectangular conductive plate 30 having one end fixed (connected) to the second terminal 32. The first terminal 31 and the second terminal 32 (terminal pair) are made of a conductive material and are connected to the electric wire 40 via

bus bars

51a and 51b, respectively.

The conductive plate 30 is formed of a bimetal formed by bonding two metal thin films (conductive members) 30a and 30b having different thermal expansion coefficients. The conductive plate 30 is mounted on the substrate 50 (bus bar 51b) with only one end connected to the second terminal 32, and the other end of the conductive plate 30 is not connected to the first terminal 31 as shown in fig. 2A in a normal state. That is, in the normal state, the protection switch 3 is in the off state (non-operating state), and the first terminal 31 and the second terminal 32 are not electrically connected.

The conductive plate 30 is configured to deform as the ambient temperature increases, and in embodiment 1, is configured to deform from the bent shape shown in fig. 2A to the linear shape shown in fig. 2B and 2C. The conductive plate 30 shown in fig. 2A to 2C is provided with, for example, a thin metal film 30a having a large thermal expansion coefficient.

The protection switch 3 is in an on state (operating state) in which the other end of the conductive plate 30 is connected to the first terminal 31 by deforming the conductive plate 30, and the connection between the

batteries

41 and 43 is closed. Therefore, the temperature at which the conductive plate 30 is deformed may be set in accordance with the specification of the semiconductor switch 2 so that the protection switch 3 operates before the semiconductor switch 2 is brought into an overheated state. The conductive plate 30 is composed of, for example, metal

thin films

30a and 30b made of an alloy of iron and nickel with manganese, chromium, copper, or the like added thereto, and the temperature at which the conductive plate 30 is deformed can be arbitrarily set according to the material of the metal

thin films

30a and 30b and the content of each material. In addition, the temperature at which the other end of the conductive plate 30 is connected to the first terminal 31 can be adjusted by adjusting the initial shape. It is preferable that the protection switch 3 is disposed in the vicinity of the semiconductor switch 2 so that the ambient temperature of the protection switch 3 becomes a temperature close to the temperature of the semiconductor switch 2.

In the protection switch 3 having the above-described configuration, for example, when a large current flows through the semiconductor switch 2 and the semiconductor switch 2 (semiconductor element) generates heat abnormally, the conductive plate 30 is deformed as the temperature of the semiconductor switch 2 increases. Then, as shown in fig. 2B, the protection switch 3 is turned on (operated) at the timing when the other end of the conductive plate 30 contacts the first terminal 31. When the protection switch 3 is operated, a large current flowing through the semiconductor switch 2 is shunted to the protection switch 3, and therefore the current flowing through the semiconductor switch 2 is reduced, and it is possible to avoid the semiconductor element and the surrounding components from being in an overheated state.

When the current flowing through the semiconductor switch 2 decreases, the temperature of the semiconductor switch 2 (semiconductor element) decreases. Therefore, in the protection switch 3 during operation, the conductive plate 30 is deformed so as to return to the original shape as the temperature of the semiconductor switch 2 decreases. That is, the conductive plate 30 having the shape shown in fig. 2B is deformed into the shape shown in fig. 2A. As shown in fig. 2A, when the other end of the conductive plate 30 is separated from the first terminal 31, the protection switch 3 is turned off to disconnect the

batteries

41 and 43, and returns to the normal state.

The

thin metal films

30a and 30b, the first terminal 31, and the second terminal 32 constituting the conductive plate 30 are preferably made of a conductive material having a small electric resistance. This can further reduce the current flowing through the semiconductor switch 2 when the protection switch 3 is operated. One end of the conductive plate 30 and the second terminal 32 are fixed by solder, screws, or the like. Preferably, the member for fixing the one end of the conductive plate 30 and the second terminal 32 is also made of a conductive material having a small electric resistance.

The first terminal 31 may be formed of a molten member that melts at a predetermined temperature. For example, the first terminal 31 may be formed of a melting member that melts at a temperature higher than the temperature at which the protection switch 3 operates (the temperature at which the conductive plate 30 deforms). In this case, as shown in fig. 2B, when the temperature of the semiconductor switch 2 (semiconductor element) further increases to reach the melting temperature of the first terminal 31 after the protection switch 3 is turned on, the first terminal 31 melts as shown in fig. 2C. As the melting member, for example, solder can be used, and when solder is used, the resistance of the first terminal 31 after melting is reduced. In the case where the semiconductor switch 2 becomes an overheated state to the extent that the melting member (first terminal 31) melts, the possibility of recovery of the semiconductor switch 2 is small. Therefore, when the first terminal 31 is melted, the current flowing through the semiconductor switch 2 can be further reduced by further reducing the resistance of the first terminal 31. When the temperature of the semiconductor switch 2 is lowered after the first terminal 31 is melted and the first terminal 31 is solidified, the other end of the conductive plate 30 and the first terminal 31 are connected by the solidified melted member (first terminal 31), and thus the on state of the protection switch 3 is maintained. Therefore, in this case, the connection between the

storage batteries

41 and 43 via the protection switch 3 can be maintained, and the power supply apparatus can perform a normal operation because the connection is not only via the semiconductor switch 2 with a low possibility of recovery. When the solder is melted and then solidified, the solder has low resistance, and therefore, is preferably used as a melting member.

In embodiment 1, the protection switch 3 is formed of a conductive plate 30 using a bimetal. The bimetal can be adjusted to be deformed at any temperature, and thus the protection switch 3 operating at any temperature can be easily realized. Therefore, the protection switch 3 can be configured to suit the environment in which it is disposed, and the switching circuit 1 and the power supply device provided with the appropriate protection switch 3 can be formed.

The conductive plate 30 is not limited to a structure using a bimetal formed by bonding two kinds of metal

thin films

30a and 30 b. In the case of a structure that deforms at an arbitrary temperature, three or more kinds of metal thin films may be bonded to form the conductive plate 30, or one kind of metal thin film may be used to form the conductive plate 30, as in the shape memory alloy.

(embodiment mode 2)

The power supply device according to embodiment 2 has the same configuration as that of the power supply device according to embodiment 1 except for the configuration of the protection switch 3, and therefore the same reference numerals are given to the same configurations and the description thereof is omitted.

Fig. 3A to 3C are sectional views showing a configuration example of a protection switch 3 according to embodiment 2. Fig. 3A shows the protection switch 3 in an off state (non-operating state), and fig. 3B and 3C show the protection switch 3 in an on state (operating state). Note that, in the protection switch 3, the same reference numerals and names are given to the same components as those in embodiment 1.

The protection switch 3 of embodiment 2 is also provided between the bus bars 51a and 51b formed on the substrate 50. The protection switch 3 of embodiment 2 includes a first terminal 31 provided on the upper surface of the bus bar 51b, a second terminal 32 provided on the upper surface of the bus bar 51a, and a conductive plate 30. The protection switch 3 according to embodiment 2 has an insulating support 33 made of an insulating material on the upper surface of the bus bar 51b at a position facing the second terminal 32 with the first terminal 31 interposed therebetween. As shown in fig. 3A, the conductive plate 30 of embodiment 2 is formed in a bent rectangular plate shape, and is attached to the substrate 50 (

bus bars

51a, 51b) in a state where one end is fixed to the second terminal 32 and the other end is fixed to the insulating support 33 and bent upward. Therefore, one end of the conductive plate 30 is electrically connected to the electric wire 40 via the second terminal 32 and the bus bar 51a, but the other end is not electrically connected to the first terminal 31 and the bus bar 51b (the electric wire 40). That is, in the normal state, the protection switch 3 is in the off state (non-operating state), and the first terminal 31 and the second terminal 32 are not electrically connected.

The conductive plate 30, the first terminal 31, and the second terminal 32 have the same configurations as the conductive plate 30, the first terminal 31, and the second terminal 32 of embodiment 1, respectively. Preferably, the one end of the conductive plate 30 and the second terminal 32 are fixed by solder, screws, or the like, and the member to be fixed is also made of a conductive material having a small electric resistance.

Since both ends of the conductive plate 30 of embodiment 2 are fixed to the second terminal 32 and the insulating support 33, when the ambient temperature increases, the conductive plate 30 is deformed from a shape bent upward as shown in fig. 3A to a shape bent downward as shown in fig. 3B and 3C. The conductive plate 30 can be deformed as described above by mounting the conductive plate 30 with the metal thin film 30a having a high thermal expansion coefficient positioned on the upper side.

In the protection switch 3 having the above-described configuration, when the semiconductor switch 2 (semiconductor element) generates heat abnormally, the conductive plate 30 deforms as the temperature of the semiconductor switch 2 increases, and as shown in fig. 3B, the protection switch 3 is turned on (operated) at the point when the lower surface of the conductive plate 30 (metal thin film 30B) contacts the first terminal 31. Thereby, the first terminal 31 and the second terminal 32 are connected to each other, and the connection between the

batteries

41 and 43 is established. In embodiment 2 as well, when the protection switch 3 is operated, since a large current flowing through the semiconductor switch 2 is shunted to the protection switch 3, the current flowing through the semiconductor switch 2 is reduced, and it is possible to avoid the semiconductor element from being in an overheated state.

In the protection switch 3 during operation, when the temperature of the semiconductor switch 2 decreases, the conductive plate 30 deforms so as to return to its original shape, and as shown in fig. 3A, the protection switch 3 is turned off and returns to the normal state at the time when the lower surface of the conductive plate 30 is separated from the first terminal 31.

In the protection switch 3 according to embodiment 2, energy required for deformation differs between the case of deforming the shape shown in fig. 3A to the shape shown in fig. 3B and the case of returning the shape shown in fig. 3B to the shape shown in fig. 3A. Therefore, by appropriately setting the thermal expansion coefficients of the metal

thin films

30a and 30b, the protection switch 3 can be switched from the on state to the off state at a temperature lower than the temperature at which the protection switch 3 is switched from the off state to the on state. Thereby, the protection switch 3 can be prevented from being frequently turned on/off.

In the protection switch 3 according to embodiment 2, as shown in fig. 3A, the conductive plate 30 is fixed to the second terminal 32 and the insulating support 33 at both ends in a bent state. Therefore, when the semiconductor switch 2 generates heat abnormally, the metal thin film 30a having a large thermal expansion coefficient presses the metal thin film 30B downward, and when the pressing force of the metal thin film 30a is equal to or greater than a predetermined value, the state shown in fig. 3B is deformed. That is, Hysteresis (hystersis) can be applied to the protection switch 3, and this deformation utilizes a phenomenon called buckling (buckling).

In embodiment 2, the first terminal 31 may be formed of a melting member that melts at a predetermined temperature (a temperature higher than the temperature at which the protection switch 3 operates). In this case, as shown in fig. 3B, when the temperature of the semiconductor switch 2 (semiconductor element) further increases to reach the melting temperature of the first terminal 31 after the protection switch 3 is turned on, the first terminal 31 melts as shown in fig. 3C. When solder is used as the melting member, the resistance of the first terminal 31 can be further reduced by melting the first terminal 31 (melting member) when the possibility of recovery of the semiconductor switch 2 is low.

In addition, when the temperature of the semiconductor switch 2 is lowered after the first terminal 31 is melted and the first terminal 31 is solidified, the lower surface of the conductive plate 30 and the first terminal 31 are connected by the solidified melted member (first terminal 31), and therefore the on state of the protection switch 3 can be maintained.

The same effects as those of the switch circuit 1 of embodiment 1 are obtained also in the switch circuit 1 of embodiment 2. In embodiment 2, the conductive plate 30 is not limited to the structure using the bimetal, and may be configured by laminating three or more kinds of metal thin films, or may be configured by one kind of metal thin film like a shape memory alloy.

The embodiments disclosed herein are considered to be illustrative in all respects, rather than restrictive. The scope of the present invention is defined not by the above-described meanings but by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

Description of the reference symbols

1 switching circuit

2 semiconductor switch

3 protective switch

30 conductive plate

31 first terminal

32 second terminal

33 insulating support

40 electric wire

41 first accumulator

43 second accumulator

30a, 30b metal film

Claims

1. A switching circuit mounted on a wire connecting a plurality of power sources, comprising:

a semiconductor switch mounted on the wire to turn on or off connection between the plurality of power sources; and

a protection switch connected in parallel with the semiconductor switch, the protection switch being deformed in accordance with a temperature rise of the semiconductor switch to turn on a connection between the power sources,

the protection switch has:

terminal pairs respectively connected to the electric wires; and

the conductive plate is formed by bonding a plurality of conductive members having different thermal expansion coefficients,

the conductive plate is connected to one of the pair of terminals and is deformed to connect the one of the pair of terminals to the other of the pair of terminals as a temperature of the semiconductor switch rises,

at least the other terminal of the pair of terminals is composed of a melting member that has conductivity and melts at a predetermined temperature, maintains connection with the conductive plate when melted and solidified in a state in which the conductive plate is in contact, and the melting member decreases in electrical resistance when melted.

2. The switching circuit of claim 1,

when the connection between the power sources is turned on, the protection switch deforms to return to its original shape as the temperature of the semiconductor switch decreases, thereby turning off the connection between the power sources.

3. The switching circuit of claim 2,

the protection switch turns off the connection between the power sources at a temperature lower than a temperature at which the connection between the power sources is turned on.

4. A power supply device is provided with:

a plurality of power supplies; and

a switching circuit as claimed in any one of claims 1 to 3.